The proposed research concerns biobehavioral approaches to the treatment of hypertension, a health problem affecting close to 40 million Americans. It constitutes an interdisciplinary effort involving the fields of internal medicine, psychiatry, and psychology. The proposed research constitutes a one-year extension of an ongoing study aimed at evaluating: (a) the effect of relaxation therapy for hypertension compared to treatment with diuretics or betablocking agents; (b) whether the effect of relaxation therapy on hypertension is additive to that of pharmacological therapy; (c) whether the effect of relaxation differs depending on concomitant drug treatment with a diuretic versus betablocking agents; (d) whether physiological or psychological variables can predict the effect of relaxation therapy. In the proposed study, 15 additional subjects will go through a nine-month program consisting of the following experimental phases: (1) placebo, (2) placebo plus relaxation, (3) chlorthalidone or atenolol only, (4) chlorthalidone or atenolol plus relaxation, (5) atenolol or chlorthalidone only, (6) atenolol or chlorthalidone plus relaxation. The order of atenolol versus chlorthalidone will be randomized. During each of the phases, patients will be seen both at the office of the relaxation therapist and at a hypertension clinic. Patients and therapists will be blind as to medication assignment. Dependent measures include office and clinic blood pressures, Avionics 24-hour ambulatory monitoring of blood pressure, and plasma renin activity. Measures on pulse and respiration rates are also obtained. Pretreatment assessment includes a brief psychological test battery consisting of the Beck Depression Scale, the Spielberger State-Trait Anxiety Inventory and the Jenkins Type A Activity Scale. The results of the study may provide guidelines for the biobehavioral management of hypertension and expand our knowledge regarding the mechanisms of the effect of relaxation therapy with hypertension.